It's no secret that license plate data is big business. Here's a demo of how these companies gather data as they troll parking lots and public streets gathering indiscriminate license plate info, looking for matches on other databases.
These technologies were originally used primarily by law enforcement, then expanded to toll road EZ-Pass type systems and security gates at parking lots. Now repo companies and other loss prevention services use the products. Many even have an infrared option for collecting data unnoticed at night. And even though it's usually blurred in the published version, Google has certainly gathered a great deal of auto data as part of their street view project.
• You Are Being Tracked: How License Plate Readers Are Being Used To Record Americans' Movements (alcu.org)